Catalysts for the manufacture of carbon fibrils and methods of use thereof

ABSTRACT

A catalyst for the production of carbon fibrils and a method for the manufacture of such a catalyst comprising contacting a fibril-forming catalyst or precursors of a fibril-forming catalyst with an effective amount of a surfactant and/or polyol. The improved carbon fibrils or carbon fibril aggregates produced using the catalyst are free of a continuous carbon thermal overcoat, with graphitic layers substantially parallel to the fibril axis, and have a substantially constant diameter from about 1.0 to 100 nanometers. The improved carbon fibrils possess enhanced dispersion in composite materials and provide enhanced electrical conductivity in those materials.

This application is a continuation of application Ser. No. 08/241,771,filed May 12, 1994 now abandoned.

BACKGROUND OF THE INVENTION

Carbon fibrils are vermicular carbon deposits having diameters less than500 nanometers. They exist in a variety of forms, and have been preparedthrough the catalytic decomposition of various carbon-containing gasesat metal surfaces.

Tennent, U.S. Pat. No. 4,663,230, describes carbon fibrils that are freeof a continuous thermal carbon overcoat and have multiple graphiticouter layers that are substantially parallel to the fibril axis. Theygenerally have diameters no greater than 0.1 micron and length todiameter ratios of at least 5. Desirably they are substantially free ofa continuous thermal carbon overcoat, i.e., pyrolytically depositedcarbon resulting from thermal cracking of the gas feed used to preparethem.

Tubular fibrils having graphitic layers that are substantially parallelto the microfiber axis and having diameters broadly between 1.0 and 100nanometers have been described in the art. Fibrils having diametersbetween 3.5 and 75 nanometers, are described in Tennent et al., U.S.Ser. No. 871,676 filed Jun. 6, 1986, refiled as continuation applicationSer. No. 593,319 filed Oct. 1, 1990, now U.S. Pat. No. 5,165,909, issuedNov. 24, 1992; (“Novel Carbon Fibrils, Method for Producing Same andCompositions Containing Same”), Tennent et al., U.S. Ser. No. 871,675filed Jun. 6, 1986, refiled as continuation application Ser. No. 492,365filed Mar. 9, 1990, now U.S. Pat. No. 5,171,560, issued Dec. 15, 1992;(“Novel Carbon Fibrils, Method for Producing Same and EncapsulatingCatalyst”), Snyder et al., U.S. Ser. No. 149,573 filed Jan. 29, 1988Jan. 28, 1988, refiled as continuation application Ser. No. 494,894,filed Mar. 13, 1990, refiled as continuation application Ser. No.694,244, filed May 1, 1991 (“Carbon Fibrils”), Mandeville et al., U.S.Ser. No. 285,817 filed Dec. 16, 1988 (“Fibrils”), Mandeville et al.,U.S. Ser. No. 285,817 filed Dec. 16, 1988, refiled as continuationapplication Ser. No. 746,065, filed Aug. 12, 1991, refiled ascontinuation application Ser. No. 08/284,855, filed Aug. 2, 1994(“Fibrils”), and McCarthy et al., U.S. Ser. No. 351,967 filed May 15,1989, refiled a continuation application Ser. No. 823,021, refiled ascontinuation application Ser. No. 117,873, refiled as continuationapplication Ser. No. 08/329,774, filed Oct. 27, 1994; (“SurfaceTreatment of Carbon Microfibers”). Methods for manufacturing catalystsfor producing carbon fibrils are described in Moy et al., U.S. Ser. No.887,307, filed May 22, 1992, refiled as continuation application Ser.No. 08/284,742, filed Aug. 2, 1994. (“Improved Methods and Catalysts forthe Manufacture of Carbon Fibrils”). All of these patents and patentapplications are assigned to the same assignee as the presentapplication and are hereby incorporated by reference.

Fibrils are useful in a variety of applications. For example, they canbe used as reinforcements in fiber-reinforced composite structures orhybrid composite structures (i.e. composites containing reinforcementssuch as continuous fibers in addition to fibrils). The composites mayfurther contain fillers such as a carbon black and silica, alone or incombination with each other. Examples of reinforceable matrix materialsinclude inorganic and organic polymers, ceramics (e.g., lead or copper).When the matrix is an organic polymer, it may be a thermoset resin suchas epoxy, bisamaleimide, polyamide, or polyester resin; a thermoplasticresin; or a reaction injection molded resin. The fibrils can also beused to reinforce continuous fibers. Examples of continuous fibers thatcan be reinforced or included in hybrid composites are aramid, carbon,and glass fibers, alone, or in combination with each other. Thecontinuous fibers can be woven, knit, crimped, or straight.

The composites can exist in many forms, including foams and films, andfind application, e.g., as radiation absorbing materials (e.g., radar orvisible radiation), adhesives, or as friction materials for clutches orbrakes. Particularly preferred are fibril-reinforced composites in whichthe matrix is an elastomer, e.g., styrene-butadiene rubber,cis-1,4-polybutadiene, or natural rubber.

In addition to reinforcements, fibrils may be combined with a matrix tocreate composites having enhanced thermal, and/or electricalconductivity, and/or optical properties. They can be used to increasedthe surface area of a double layer capacitor plate or electrode. Theycan also be formed into a mat (e.g., a paper or bonded non woven fabric)and used as a filter, insulation (e.g., for absorbing heat or sound),reinforcement, or adhered to the surface of carbon black to form “fuzzy”carbon black. Moreover, the fibrils can be used as an adsorbent, e.g.,for chromatographic separations.

Fibrils are advantageously prepared by contacting a carbon-containinggas with a metal catalyst in a reactor at temperature and otherconditions sufficient to produce them with the above-describedmorphology. Reaction temperatures are 400-850° C., more preferably600-700° C. Fibrils are preferably prepared continuously by bringing thereactor to the reaction temperature, adding metal catalyst particles,and then continuously contacting the catalyst with the carbon-containinggas.

Examples of suitable feed gases include aliphatic hydrocarbons, e.g.,ethylene, propylene, propane, and methane; carbon monoxide; aromatichydrocarbons, e.g., benzene, naphthalene, and toluene; and oxygenatedhydrocarbons.

Preferred catalysts contain iron and, preferably, at least one elementchosen from Group V (e.g., vanadium), Group VI (e.g. molybdenum,tungsten, or chromium), Group VII (e.g., manganese), Group VIII (e.g.cobalt) or the lanthanides (e.g., cerium). The catalyst, which ispreferably in the form of metal particles, may be deposited on asupport, e.g., alumina and magnesia.

The carbon fibrils produced by these catalysts have a length-to-diameterratio of at least 5, and more preferably at least 100. Even morepreferred are fibrils whose length-to-diameter ratio is at least 1000.The wall thickness of the fibrils is about 0.1 to 0.4 times the fibrilexternal diameter.

The external diameter of the fibrils is broadly between 1.0 and 100nanometers and preferably is between 3.5 and 75 nanometers. Preferably alarge proportion have diameters falling within this range. Inapplications where high strength fibrils are needed (e.g., where thefibrils are used as reinforcements), the external fibril diameter ispreferably constant over its length.

Fibrils may be prepared as aggregates having various macroscopicmorphologies (as determined by scanning electron microscopy) in whichthey are randomly entangled with each other to form entangled balls offibrils; or as aggregates consisting of bundles of straight to slightlybent or kinked carbon fibrils having substantially the same relativeorientation in which the longitudinal axis of each fibril (despiteindividual bends or kinks) extends in the same direction as that of thesurrounding fibrils in the bundles; or, as aggregates consisting ofstraight to slightly bent or kinked fibrils which are loosely entangledwith each other to form a more open structure. In the open structuresthe degree of fibril entanglement is greater than observed in theparallel bundle aggregates (in which the individual fibrils havesubstantially the same relative orientation) but less than that ofrandom entangled aggregates. All of the aggregates are dispersable inother media, making them useful in composite fabrication where uniformproperties throughout the structure are desired. In the parallel bundleaggregates the substantial linearity of the individual fibril strands,which are also electrically conductive, makes the aggregates useful inEMI shielding and electrical applications.

The macroscopic morphology of the aggregate is influenced by the choiceof catalyst support. Spherical supports grow fibrils in all directionsleading to the formation of random, entangled aggregates. Parallelbundle aggregates and aggregates having more open structures areprepared using supports having one or more readily cleavable planarsurfaces, e.g., an iron or iron-containing metal catalyst particledeposited on a support material having one or more readily cleavablesurfaces and a surface area of at least 1 square meters per gram.

Preferred support materials include the various aluminas(stoichiometries corresponding to Al₂O₃.H₂O or AlO.OH), or gamma-alumina(Al₂O₃) or magnesia (MgO). Additionally, hydrous aluminas(stoichiometries corresponding to Al(OH)₃ or Al₂O₃.3H₂O), calcinedlightly at temperatures below about 800° C. yield activated aluminas(Al₂O₃.H₂O) which retain the platelet morphology of the initial hydrousalumina. These result in highly preferred supports. Such materials arecommercially available, e.g., from ALCOA (hydrous and activatedaluminas) and Martin Marietta (magnesia). The activated alumina supportsyield primarily parallel bundle aggregates, while the magnesia supportsyield primarily the more open aggregates. Spherical gamma aluminaparticles, which yield random entangled aggregates, are available fromDegussa.

It is believed that deposition of fibril growth catalysts on supportshaving planar surfaces allow the fibrils to orient themselves with eachother as they grow, creating a “neighbor effect”. This leads then to aparallel bundle fibril aggregate in which the areas of all of theindividual fibrils have the same relative orientation. The magnesiasupports, although having readily cleavable planar surfaces, yieldprimarily lightly entangled, open net fibril aggregates because theybreak apart more readily into smaller particles than the activatedalumina support during fibril growth, resulting in aggregates that areless ordered than the parallel bundle aggregates but more ordered thanthe tightly entangled fibril balls. The more readily the oxide andsupport can form a mixed oxide at the interface between them, the morelikely the support is to break apart.

Further details regarding the formation of carbon fibril aggregates maybe found in the disclosure of Snyder et al., U.S. patent applicationSer. No. 149,573, filed Jan. 28, 1988, refiled as continuationapplication Ser. No. 494,894, filed Mar. 13, 1990, refiled ascontinuation application Ser. No. 694,244, filed May 1, 1991; and PCTApplication No. U.S. 89/00322, filed Jan. 28, 1989 (“Carbon Fibrils”) WO89/07163, and Moy et al., U.S. patent application Ser. No. 413,837 filedSep. 28, 1989, refiled as continuation application Ser. No. 855,122,filed Mar. 18, 1992, refiled as continuation application Ser. No.08/284,917, filed Feb. 27, 1995, PCT Application No. U.S. 90/05498,filed Sep. 27, 1990 (“Fibril Aggregates and Method of Making-Same”) WO91/05089, and Tennent, et al, U.S. patent application Ser. No. 057,328,filed May 5, 1993 (“Three Dimensional Macroscopic Assemblages ofRandomly Oriented Carbon Fibrils and Composites Containing Same”), allof which are assigned to the same assignee as the invention here and arehereby incorporated by reference.

Fibrils are increasingly important in a variety of industrial uses.While known methods of manufacture permit production of small quantitiesof fibrils, it is important to improve these methods, and in particularthe catalysts used in those methods, to increase the yield of fibrils,to improve their quality and to lower their cost of production. It isalso desirable to produce carbon fibrils of improved purity.

Furthermore, it is desirable to produce fibrils with enhanceddispersability and electrical conductivity properties. It is importantto improve the ability of fibrils to disperse in media. In particular,it is desirable to increase the ability of fibrils to disperse inthermoplastics or engineering plastics. Dispersion of fibrils into mediaalso imparts enhanced electrical conductivity properties to said media.

OBJECTS OF THE INVENTION

It is thus a primary object of the invention to provide improvedcatalysts for the production of fibrils.

It is a further object of the invention to provide catalysts for theproduction of fibrils that are more readily dispersed in media.

Another object of this invention is to provide catalysts yieldingfibrils capable of imparting enhanced electrical conductivity propertiesto a media.

It is also an object of the invention to increase the yield andproductivity of fibril-producing catalysts.

It is still a further object of the invention to provide improvedmethods of preparing fibril-producing catalysts.

It is yet another object of this invention to improve the quality anduniformity of fibrils and aggregates thereof.

It is still a further related object of the invention to improve theeconomics and reliability of fibril manufacture.

SUMMARY OF THE INVENTION

Methods have now been found which yield catalysts that producesubstantially superior carbon fibrils and carbon fibril aggregates.These catalysts can be obtained by contacting a fibril-forming catalystor precursors of a fibril-forming catalyst with an effective amount of asurfactant and/or polyol. The method is preferably carried out byprecipitating a fibril-producing metal oxide or compound from an aqueoussolution onto slurried particles of a support material in the presenceof surfactant and/or polyol.

This invention further provides a catalyst for the production of carbonfibril aggregates produced by the method of contacting a fibril-formingcatalyst or precursors of a fibril-forming catalyst with an effectiveamount of a surfactant and/or polyol. Preferably, the catalyst is formedby precipitating a fibril-producing metal oxide or compound from anaqueous solution onto slurried particles of a support material in thepresence of a surfactant and/or polyol.

Also provided by this invention is a volume of carbon fibrils comprisinga multiplicity of fibrils that are free of a continuous thermal carbonovercoat, have graphitic layers that are substantially parallel to thefibril axis, and possess a substantially constant diameter. In apreferred embodiment the diameter of the fibrils is from about 4.0 toabout 20 nanometers.

The improved methods of making fibril-forming catalysts and the improvedcatalysts themselves produce superior carbon fibrils and carbon fibrilaggregates possessing enhanced dispersion and electroconductivityqualities. The resultant carbon fibrils exhibit improved characteristicsthat enable fibrils or fibril aggregates to disperse better in a media.Additionally, the carbon fibrils produced by the improved catalystsprovided by this invention impart increased electroconductivity to themedia in which they are dispersed.

DETAILED DESCRIPTION OF THE INVENTION

The term “fibril-forming catalyst” is used to refer collectively tocatalysts for forming discrete carbon fibrils, carbon fibril aggregatesor both.

The term “carbon fibrils” when referring to products is used to refercollectively to both discrete carbon fibrils and carbon fibrilaggregates, unless the context indicates a different meaning.

This invention provides a method for the manufacture of a catalyst forthe production of carbon fibrils comprising contacting a fibril-formingcatalyst or precursors of a fibril-forming catalyst with an effectiveamount of a surfactant and/or polyol. The method for the manufacture ofa catalyst for the production of carbon fibrils preferably comprises thesteps of forming an aqueous solution of a Period Four transition metaliron compound or a Period Four transition metal and molybdenum compound,forming a slurry of catalyst support particles comprising alumina and/ormagnesia particles, precipitating an iron compound or iron andmolybdenum compounds onto the alumina and/or magnesia particles in thepresence of a surfactant and/or polyol, and then processing the slurryto produce a fibril-forming catalyst.

Preferably, the surfactant is stable at pH levels from about 3 to about9 and does not itself cause precipitation of ferric oxide or compounds.Members from the usual classes of anionic, cationic or non-ionicsurfactants are effective. In one embodiment of the invention thesurfactant is non-ionic. The preferred non-ionic surfactants includeethoxylated alkyl phenols, other ethoxylated and/or propoxylatedderivatives, and functionalized organosiloxanes.

In another embodiment of this invention, the surfactant is ananti-foaming agent. Examples of anti-foaming agents include substitutednonylphenols, organo-modified polysiloxanes, and emulsified siliconeformulations.

In other preferred embodiments of the invention the surfactant can beethylene oxide-propylene oxide copolymers, substituted alkyl phenols,alkali metal salts of polymeric carboxylic acids, derivatizedpolyalkylsiloxanes, ethoxylated amines, quaternary amine salts andderivatized nitrogen compounds (such as imidazoles and pyrimidines).

Examples of preferred polyols used in certain embodiments of thisinvention include glycerine, sucrose and polyethylene glycol.

A preferred method of manufacturing a catalyst for the production ofcarbon fibrils comprises forming an iron or iron and molybdenum saltsolution, forming a slurry of catalyst support particles comprisingalumina particles, precipitating iron or iron and molybdenum oxide ontosaid alumina particles in the presence of a surfactant, anti-foam agentor polyol at a pH of about 6, then filtering and washing the slurryfollowed by drying at about 140° C. to about 200° C. yield afibril-forming catalyst.

Embodiments of the invention include, but are not limited to, addingsoluble surfactant and/or anti-foam and/or polyol to the iron or ironand molybdenum aqueous solution; adding surfactant and/or anti-foamand/or polyol to the alumina or magnesia slurry; and adding surfactantand/or anti-foam and/or polyol to both the iron or iron/molybdenumaqueous solution and the slurry of alumina or magnesia.

This invention also provides a catalyst for the production of carbonfibrils that are produced by contacting a fibril-forming catalyst orprecursors of a fibril-forming catalyst with an effective amount of asurfactant and/or polyol.

Further provided by this invention is a volume of carbon fibrilscomprising a multiplicity of fibrils having a morphology consisting oftubes that are free of a continuous thermal carbon overcoat, graphiticlayers that are substantially parallel to the fibril axis, and asubstantially constant diameter. Preferably, the diameter of the fibrilsis from about 4.0 to about 20 nanometers.

The immediate improvement in the catalysts of this invention are seen inthe fibrils which they produce. They make more uniform fibrils ofsmaller diameter (from about 4.0 to about 20 nanometers most preferably7-10 namometers) thereby increasing the surface area of fibrils. Inaddition, the aggregates, which resemble parallel bundle aggregates, aremuch smaller (approximately 0.1-1 micron, and some as small as about 0.1micron). This results in fibril aggregates which are much easier todisperse and thereby impart higher electrical conductivity to thedispersed medium. The smaller aggregates also allow for dispersions offibrils to nearly the individualized state (absence of bundles or otherfibril aggregates) leading to open, three-dimensional network mats.

While not wishing to be bound by any theory, it is believed that theimproved properties of the fibrils (i.e., improved dispersibilities inthermoplastics and/or polymers, and improved electrical conductivitiesin these formulations, and the ability to make open, three-dimensionalnetwork mats from superior dispersions) results from better dispersionof iron or iron/molybdenum oxide particles which are deposited on thesurface of the support in the presence of surfactant, anti-foam agent orpolyol. The surfactant, anti-foam or polyol interacts with the surfaceof the precipitated iron or iron/molybdenum oxide to decreaseparticle-particle interaction, stabilizing the small aggregate particlesby retarding the growth or sintering into larger aggregates. The smalleriron or iron/molybdenum particles also lead to fibrils with smalleraverage diameters.

One class of surfactants used (although not limited to) are non-ionic,particularly alkylated phenols, ethoxylated alkyl phenols, alkoxylatedderivatives and functionalized organosiloxanes. Examples of commercialsurfactants which may be classified more narrowly as “dispersants” or“anti-foam agents” are Triton X-100 (ethoxylated nonylphenol, Rohm &Haas) or Anti-Foam A (Organomodified polysiloxane, Sigma).

Again, while not wishing to be bound by any particular theory, it isbelieved that a second pathway by which these catalysts yield improvedfibril aggregates is by facilitating the breaking apart of the support(activated alumina or magnesia) particles. The preferred support forthese catalysts are flat, planar hydrous alumina (Al(OH)₃) plateletswhich have been lightly calcined from about 225 to about 800° C. to acomposition approaching activated alumina, Al₂O₃.H₂O, without anysubstantial change in the platelet structure. The weight loss oncalcination is 27-33 wt % H₂O.

The aggregate particles of the support are made up of submicron, flatplatelets which are loosely held together into aggregates by bindingthrough surface hydroxyl ions. Iron, or iron/molybdenum oxide particlesare deposited on the surface of and the crevices between platelets.These platelets then separate and break apart into smaller plateletsfrom the heat of reaction and the force of the fibrils. The planarstructure of the support then orients the individual growing fibrilsinto a CY macromorphology.

The use of surfactants or polyols are believed to decrease theinter-platelet or inter-particle attractions by exchanging, neutralizingor binding surface hydroxy groups which then allows the plates to becleaved more easily yielding smaller plates and thereby smaller fibrilbundles (sub-micron in size). These smaller bundles (0.1-1 micron) arethen easier to disperse than larger bundles (0.5-2 micron) obtained withconventional catalysts.

Again, while not wishing to be bound by any particular theory, it isbelieved that a second pathway by which these catalysts give improvedperformance is by facilitating the breaking apart of alumina particles.The preferred slurry support for catalysts are hydrous aluminas(Al(OH)₃) which have been lightly calcined to greater than about 27%weight loss.

The aggregate particles of the support are made up of submicron, flatplates which are held together by binding through surface hydroxy ions.Iron oxide particles are deposited on the open surfaces and in thecrevices between platelets. As fibrils undergo growth the planarsurfaces orient the individual fibrils in the parallel bundlemorphology.

The resulting bundles are easier to disperse than conventional largerbundles because the sub-micron dimensions of the plates produce verysmall bundles (diameters as small as about 0.1 micron). Additionally,the use of surfactants to decrease the inter-particle attractions byexchanging, neutralizing or binding surface hydroxy groups, allows theplates to be cleaved more readily, yielding smaller plates and smallerbundles.

Examples of surfactants, which may also be more narrowly defined asDispersants or Anti-Foams are Triton X-100 or Tamol-731 (Rohm & Haas),EPO-61 (ethylene oxide-propylene oxide co-polymer from Harcros), HL-36or Anto-Foam 204 (non-silicone Anti-Foams available from Harcros andSigma, respectively).

Other preparations combine a surfactant, anti-foam agent, or polyoladded through the iron/molybdenum solution and a surfactant added to theslurry of alumina support. The precipitation is carried out as describedbelow. These preparations use other types of surfactants besidesantifoams. Other surfactants were formulations of ethyleneoxide-propylene oxide co-polymers, substituted alkylphenols, or alkalimetal salts of polymeric carboxylic acids. Other surfactant formulationsalso include derivatized polyalkylsiloxanes, ethoxylated amines,quaternary amine salts, derivatized nitrogen compounds (e.g. imidazoles,pyrimidines) or any of the class of surfactants (cationic, anionic ornon-ionic) which are stable at pH levels from about 3 to about 9 and bythemselves do not cause precipitation of ferric ions.

Method

All the catalysts were prepared by precipitation of iron and molybdenumoxides at a controlled pH. The surfactant or polyol could be added tothe Fe/Mo salt solution from which the oxides were precipitated, to thealumina slurry, or both. The support for all catalyst examples was ahydrous alumina (Al(OH)₃ or Al₂O₃.3H₂O) available from Alcoa, designatedH-705, which had been lightly calcined between 280-600° C to give about27-33 percent weight loss to give an activated alumina with compositionAl₂O₃.H₂O).

This invention is illustrated in the examples which follow. The examplesare set forth to aid in understanding the invention but are not intendedto and should not be construed to in any way, limit the scope of theclaims.

EXAMPLE I

A catalyst was made by precipitating iron/molybdenum oxides onto AlcoaH-705 (a hydrous alumina) which had been lightly calcined to about 27percent weight loss. Precipitation of the oxides was done at a pH ofabout 6.0 by concurrent addition of ammonium carbonate at relative ratesto maintain the pH at about 6.0.

The catalyst slurry was filtered and washed, dried at 140° C. andcalcined at 400° C. The yield of fibrils was 24.7 times the weight ofcatalyst.

EXAMPLE II Comparative Example: Catalyst Without Surfactant

In an indented multi-neck, 2 l.r.b. flask, 41.4 g activated alumina madefrom Alcoa H-705 (calcined to 33% weight loss) was slurred with 39.5 gammonium acetate solution (65% weight in water) and 1000 cc DI water.The slurry was well-stirred for 30 minutes using an overhead stirrer.

Ammonium paramolybdate ((NH₄)₆Mo₇O₂₄.4H₂O), 2.60 g was dissolved in 50cc DI water and then added with stirring to 86.1 g of ferric nitratesolution (37.5% weight, 8.65% Fe content in DI water) to form a clear,dark red-brown solution (A).

With a pH meter probe immersed in the alumina slurry and with rapidstirring, solution A was added dropwise concurrently with a 20% weightsolution of ammonium carbonate at relative rates of each sufficient tomaintain the bulk pH at 6.0±0.2. The mixed oxides of Fe(III) and Mo(VI)were precipitated immediately and adsorbed onto the surface of thealumina particles. After addition of the reagents, the slurry wasstirred for 30 minutes.

The slurry was vacuum filtered and the filter cake was washed with atotal of 1.5 l DI water either on the filter or by twice reslurrying andrefiltering. The washed filter cake was a homogeneous, brown solid withno indication of striated layers or inhomogeneity.

The solids were dried in a forced air oven at 180° C. overnight.Recovery of dried catalyst was 54.7 g. The catalyst was ground by handand sieved through a 100 mesh screen.

The catalyst was tested. The result is summarized in Table 1.

EXAMPLE III

The procedure used was identical to Ex. 2 except for the Fe/Mo solution,which contained 4.0 g. silicone Anti-Foam A emulsion (Sigma). Thesolution, with emulsion, was mixed in a Waring blender at low speed for1 min. prior to addition to the alumina slurry. The resulting emulsionwas stable for several hours with no indication of separation. Recoveredcatalyst was 53.1 g.

EXAMPLE IV

The procedure used was identical to Ex. 2 except that the Fe/Mo solutioncontained 4.0 g. glycerin. The resulting solution was clear with noprecipitation. Recovered catalyst was 51.1 g.

EXAMPLE V

The procedure used was identical to Ex. 2 except that the Fe/Mo solutioncontained 4.0 g. sucrose. The resulting solution was clear with noprecipitation. Recovered catalyst was 48.2 g.

EXAMPLE VI

The procedure was identical to Ex. 2 except that the Fe/Mo solutioncontained 4.0 g Triton X-100 (alkylated nonyl phenol available from Rohm& Haas). The resulting solution was clear with no sign of precipitation.Recovered catalyst was 51.2 g.

EXAMPLE VII

40 g activated alumina made by lightly calcining ALCOA H-705 (33% weightloss) was slurried with 30 g ammonium acetate solution (65% weight) and1 liter DI water. Slurry was rapidly stirred for 30 min.

81 g of 37.5% ferric nitrate solution was mixed in a Waring blender witha mix containing 1.0 g Polysiloxane 200, 0.65 cp (Aldrich), 0.12 g.Triton X-100 (Rohm-Haas) and 100 cc DI water. The resulting emulsion wasstable for several hours without separation.

Precipitation and subsequent work-up was carried out as in Ex. 2.Recovered catalyst was 49.8 g.

EXAMPLE VIII

The procedure was similar to Ex. 2. 80 g activated alumina made bylightly calcining ALCOA H-705 (33% weight loss) was slurried with 76.3 gammonium acetate (65% weight solution) and 1 liter DI water. Slurry wasrapidly stirred by an overhead stirrer for 30 min.

The Fe/Mo solution (166.4 g 37.5% ferric nitrate solution plus 5.0 gammonium paramolybdate dissolved in 100 cc DI water) also contained 7.0g glycerol and 6.0 g silicone Anti-Foam A emulsion. The formulation wasmixed in a Waring blender for 1 min; resulting emulsion was stable forseveral hours without separation. Precipitation and subsequent work-upwas similar to Ex. 2. A total of 3 l. DI water was used to wash thefilter cake. Recovered catalyst was 106.4 g.

Examples 10-15 describe the preparation of catalysts by addition ofsurfactant or polyol to the alumina dispersion. The results of catalysttests are listed in Table 2.

EXAMPLE IX

The procedure used was identical to Ex. 2 except that the alumina slurry(Alcoa H-705, lightly calcined to 27% weight loss) also contained 16.0 gSigma Anti-Foam 204 (organic, non-silicone). The slurry was well-mixedwith an overhead stirrer for 1 hr prior to precipitation of Fe/Mooxides. The precipitation, filtration, washing, drying, grinding andsieving procedure was identical to Ex. 2. Recovered catalyst was 52.89g.

EXAMPLE X

The procedure similar to Ex. 10 was used, with the exception that thealumina slurry contained 8.0 g Sigma Anti-Foam 289 (non-silicone)instead of Anti-Foam 204. The remainder of the procedure was identical.Recovered catalyst was 53.36 g.

EXAMPLE XI

The procedure similar to Ex. 10 was used, with the exception that thealumina slurry contained 4.0 g Tamol 731 (Rohm & Haas, Na salt ofpolymeric carboxylic acids) instead of Sigma Anti-Foam 204. Theremainder of the procedure was identical. Recovered catalyst was 51.00g.

EXAMPLE XII

The procedure similar to Ex. 10 was used, with the exception that thealumina slurry contained 16.0 g Anti-Foam HL-36 (Harcros) instead ofSigma Anti-Foam 204. The remainder of the procedure was identical.Recovered catalyst was 51.37 g.

EXAMPLE XIII

The procedure similar to Ex. 10 was used, with the exception that thealumina slurry contained 16.0 g EPO-61 (ethylene oxide-propyleneco-polymer, Harcros) instead of Sigma Anti-Foam 204. The remainder ofthe procedure was identical. Recovered catalyst was 48.89 g.

EXAMPLE XIV

The procedure similar to Ex. 10 was used, with the exception that thealumina slurry contained 8.0 g Polyethylene Glycol 400 (Aldrich) insteadof Sigma Anti-Foam 204. The remainder of the procedure was identical.Recovered catalyst was 51.02 g.

Examples 16-20 describe the preparation of catalysts using surfactantsor polyols or both by addition to both the ferric nitrate/ammoniummolybdate solution and the alumina dispersion. Test results for thesecatalysts are summarized in Table 2.

EXAMPLE XV

In a procedure similar to Ex. 2, a catalyst on activated alumina madefrom Alcoa H-705 by lightly calcining to 27% weight loss was prepared.In this example, the Fe/Mo solution also contained 4.0 g Sigma Anti-FoamA emulsion. The alumina slurry also contained 16.0 g. Sigma Anti-foam204. The remainder of the procedure was identical. Recovered catalystwas 52.05 g.

EXAMPLE XVI

2 kg alumina made from Alcoa H-705, lightly calcined to 33% weight losswas slurried with 1.5 kg of ammonium acetate solution (65% weight), 50 gSigma Anti-Foam 204 and 12 gal DI water in a 30 gal reactor alsoequipped with a Lightnin 4000 top stirrer and an Omega pH probe andcontroller which delivered a 20% weight solution of ammonium carbonate.The controller was set to maintain the bulk pH of the slurry at 6.0±0.2.The pH of the slurry was adjusted to 6.0.

In a 5 l flask, 4.2 kg ferric nitrate solution (37.5% weight, 8.65%weight Fe) was mixed with a solution of 133 g ammonium paramolybdatedissolved in 1 l DI water and 25 g Sigma Anti-Foam A emulsion. Themixture was diluted to 6.0 l and stirred with an overhead stirrer for 30min. A stable emulsion was obtained. The emulsion was loaded into a 6gal feed tank.

The Fe/Mo emulsion was fed into the reactor at the rate of 5 min/l withrapid stirring. The pH was kept at 6.0±0.2 by addition of the 20% weightammonium carbonate which was controlled by the Omega pHprobe/controller.

After the addition of reagents, the slurry was stirred for 1 hr. Thesolids were collected and washed in a plate and frame filter press. Thefilter cake was washed until the conductivity of the effluent wash waterwas less than 1.0 mS.

The filter cake was dried at 275° C. in a forced air oven overnight.Recovered catalyst was 2515 g. The dried catalyst was ground in a hammermill and sieved to −100 mesh.

EXAMPLE XVII

In a procedure similar to Ex. 16, 80.0 g activated alumina made fromAlcoa H-705, lightly calcined to 33% weight loss, was slurried with 76.0g ammonium acetate solution (65% weight), 10.7 g Harcros EPO-61surfactant and 1 l DI H₂O in a 3-neck flask. The slurry was well-stirredfor 0.5 hr.

In a separate vessel, 170.0 g ferric nitrate solution (37.5% weight,8.65% weight Fe) was mixed with a solution of 5.3 g ammonium molybdatein 100 cc DI water and 4.0 g Sigma Anti-Foam A emulsion. The mixture wasstirred vigorously to yield a stable emulsion.

The remainder of the procedure was identical. Recovered catalyst was105.8 g.

EXAMPLE XVIII

In a procedure similar to Ex. 16, 50.0 g activated alumina made fromAlcoa H-705, lightly calcined to 33% weight loss, was slurried with 48.0g ammonium acetate solution (65% weight), 10.0 g Harcros Anti-Foam HL-36and 1.5 l DI water. The mixture was stirred vigorously for 30 min.

Separately, 106.0 g ferric nitrate solution (37.5% weight) was mixedwith a solution containing 3.3 g ammonium molybdate in 50 cc DI water,and 3.0 g Sigma Anti-foam A emulsion. The mixture was stirred vigorouslyto give a stable emulsion.

The precipitation of Fe/Mo oxides and subsequent work-up were identicalto Ex 16. Recovered catalyst was 63.39 g.

EXAMPLE XIX

The procedure was identical to Ex. 16, except that the Fe/Mo solutioncontained 4.0 g glycerin instead of Sigma Anti-Foam A emulsion. Theremainder of the preparation was the same as Ex. 16. Recovered catalystwas 52.11 g.

EXAMPLE XX

Tests were conducted to measure the conductivities of the fibrils.

There were two parts to the procedure: 1), sample preparation; and 2),sample measurement. A time gap between the two parts allowed forequilibration the sample temperature; this time gap was as long as wasconvenient.

The mamp measurement can be done using any conventional electrodeassembly at a voltage gradient of 15 v/cm. The actual electrodes were 5sq-cm and were placed 1 cm apart.

50 g of steel balls were placed in a bottle containing. fibrils and wereshaken on the Red Devil for 1 min. 0.200 g of fibrils were placed in aplastic beaker (Falcon). 200 g CVS mineral oil were added to a blendercup. The fibrils were then added to the blender and blended for 5 min atspeed 7. Contents of the blender were transfered back into the plasticcup; the cup was then covered and placed into a water bath (already setto 25° C.).

Samples were left for 1 hr to equilibrate the temperature.

While samples were still in the water bath at −25° C., the voltage onthe power supply to the cell was set at 15 v. The temperature of thesample was adjusted to 25.0° C. by adding hot or cold water to the bath;the sample was then placed in the Red Devil shaker. The sample wasshaken for exactly 30 sec. The sample was immediately taken to theconductivity bench; 30 seconds later the electrodes were placed into thecup; a reading (ma current) was taken after 1.0 min. Conductivity wascalculated as follows:

conductivity (kohm-cm)=75/current (in ma)

EXAMPLE XXI

The productivities of the catalyst for producing carbon fibrils wasdetermined in a 1 inch quartz tube reactor using the followingprocedure: a 1 inch quartz tube was fitted with a ¼ inch thermocoupletube inserted through the bottom. At the tip of the thermocouple tube aplug of quartz wool that had been previously weighed was placed whichpermitted passage of gas, but not particles of catalyst or fibrilsgrowing on the catalyst. The top of the quartz tube was fitted with agas line which allowed for a downflow addition of one or more gases, anda modified ball valve which allowed addition of a given charge ofpowdered catalyst. One opening of the ball was closed off so that itbecame a cup or sealed cylinder. Catalyst could then be loaded into thecup and the valve assembly sealed. The contents of the cup could then beadded to the gas stream without air contamination by turning the valve.

A thermocouple was inserted upward into the thermocouple tube to monitorthe reactor temperature. The tube reactor was heated to 680° C. in anArgon stream to purge the reactor after which the gas stream wasswitched to a mixture of hydrogen and ethylene at a flow rate of 400 and200 cc/min under standard conditions. A weighed charge of catalyst(about 0.02-0.05 g) was dropped into the downflow gas onto the quartzplug. The reactor was maintained at temperature for about 20 minutes,after which the reactor was cooled in argon and emptied. The weight ofcarbon fibrils produced was calculated from the total recovered weightand the known weights of the quartz wool plug and the catalyst fed. Theyield of carbon fibril, or productivity, was calculated as the weight ofcarbon produced per weight of catalyst or per weight of iron in thecatalyst.

TABLE 1 COMPARATIVE EXAMPLE: CATALYST WITHOUT SURFACTANT EXAMPLE #DESCRIPTION RESISTIVITY 2 No surfactant 660

TABLE 2 MODIFIED CATALYSTS EXAMPLE # DESCRIPTION RESISTIVITY 3 33%,Anti-Foam A(A-A) 40 4 27%, Glycerine 60 5 27%, Sucrose 80 6 27%, TritonX-100 100 7 33%, Trit X/Silicone 114 8 33%, A-A + Glycerine 45 9 27%,Anti-Foam 204 100 10 27%, Anti-Foam 289 400 11 27%, Tamol 731 90 12 27%,Anti-Foam HL-36 75 13 27%.EP061 70 14 27%, Polyethylene Gly 170 15 27%,A-A + A-204 39 16 33%, A-A + A-204 75 17 33%, A-A + EP061 215 18 33%,A-A + HL-36 70 19 33%, Glycerin + A-204 80

What is claimed is:
 1. A method for the manufacture of a catalyst forthe production of carbon fibrils comprising forming a fibril-formingcatalyst or a precursor of a fibril-forming catalyst in the presence ofan effective amount of a surfactant and/or polyol to increase the yieldof the carbon fibrils and to improve the dispersion and electrochemicalproperties of the carbon fibrils, wherein said fibril-forming catalystcomprises metal particles dispersed on a catalyst support particle, thecatalyst support particle selected from the group consisting of aluminaor magnesia particles, and the metal particles comprise iron andoptionally at least one element chosen from V, Nb, Ta, Cr, Mo, W, Mn,Tc, Re, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt or the lanthanides.
 2. A methodas recited in claim 1, wherein the surfactant is selected from the groupconsisting of ethylene oxide-propylene oxide copolymers, substitutedalkyl phenols, alkali metal salts or polymeric carboxylic acids,polyalkylsiloxanes, ethoxylated amines, quaternary amine salts,imidazoles and pyrimidines.
 3. The method as recited in claim 1, whereinthe formulation of said fibril-forming catalyst comprises the steps of:(a) forming an aqueous solution of a compound comprising iron andoptionally at least one element chosen from V, Nb, Ta, Cr, Mo, W, Mn,Tc, Re, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt or the lanthanides; (b) forming aslurry of catalyst support particles selected from the group consistingof alumina and magnesia particles; (c) precipitating the compound ofstep (a) onto said support particles; and (d) recovering said supportparticles from said slurry to produce said fibril-forming catalyst.
 4. Amethod as recited in claim 1, wherein the surfactant is a non-ionicsurfactant.
 5. A method as recited in claim 4, wherein the non-ionicsurfactant is an alkylated phenol, an ethoxylate surfactant, or afunctionalized organosiloxane.
 6. A method as recited in claim 1,wherein the surfactant is an anti-foaming agent.
 7. A method as recitedin claim 6, wherein the anti-foaming agent is a substituted nonylphenol,a polyalkylsiloxanes or an emulsified silicone formulation.
 8. A methodas recited in claim 1, wherein the surfactant is stable at pH levelsfrom about 3 to about 9 and does not itself cause precipitation of ametal ion.
 9. A method as recited in claim 1, wherein the polyol isselected from the group consisting of glycerine, sucrose andpolyethylene glycol.
 10. A method as recited in claim 1, wherein thesurfactant is anionic.
 11. A method as recited in claim 1, wherein thesurfactant is cationic.
 12. A method for the manufacture of a catalystfor the production of carbon fibrils comprising the steps of: (a)forming an aqueous solution of a compound comprising iron and optionallyat least one element chosen from V, Nb, Ta, Cr, Mo, W, Mn, Tc, Re, Ru,Os, Co, Rh, Ir, Ni, Pd, Pt or the lanthanides; (b) forming a slurry ofcatalyst support particles selected from the group consisting of aluminaand magnesia particles; (c) precipitating the compound of step (a) ontosaid support particles in the presence of a surfactant and/or polyol;and (d) recovering said support particles from said slurry to produce afibril-forming catalyst.
 13. A method as recited in claim 12, whereinthe aqueous solution of step (a) further comprises a soluble polyol. 14.A method as recited in claim 12, wherein the aqueous solution of step(a) further comprises a surfactant.
 15. A method as recited in claim 12,wherein the slurry of step (b) further comprises a surfactant.
 16. Amethod as recited in claim 12, wherein the slurry of step (b) furthercomprises a polyol.
 17. A method as recited in claim 12, wherein theaqueous solution of step (a) and the slurry of step (b) further comprisea surfactant.
 18. A method as recited in claim 12, wherein the aqueoussolution of step (a) and the slurry of step (b) further comprise apolyol.
 19. A method for the manufacture of a catalyst for theproduction of carbon fibrils comprising the steps of: (a) forming aniron salt solution; (b) forming a slurry of catalyst support particlesselected from the group consisting of alumina and magnesia particles;(c) precipitating iron oxide onto said support particles in the presenceof an anti-foaming agent; (d) filtering and washing the slurry; and (e)drying the slurry.
 20. A catalyst for the production of carbon fibrilsproduced by the method of forming a fibril-forming catalyst orprecursors of a fibril-forming catalyst in the presence of an effectiveamount of a surfactant and/or polyol to increase the yield of the carbonfibrils and to increase the dispersion and electrochemical properties ofthe carbon fibrils, wherein said fibril-forming catalyst comprises metalparticles dispersed on a catalyst support particle, the support particleselected from the group consisting of alumina and/or magnesia particles,and where the metal particles comprise iron and optionally at least oneelement chosen from V, Nb, Ta, Cr, Mo, W, Mn, Tc, Re, Ru, Os, Co, Rh,Ir, Ni, Pd, Pt or the lanthanides.
 21. A catalyst for the production ofcarbon fibrils produced by a method comprising the steps of: (a) formingan aqueous solution of an iron compound or iron and molybdenumcompounds; (b) forming a slurry of catalyst support particles comprisingalumina particles and/or magnesia particles; (c) precipitating an ironcompound or iron and molybdenum compounds onto said alumina and/ormagnesia particles in the presence of a surfactant and/or polyol; and(d) recovering said catalyst support particles from said slurry toproduce a fibril-forming catalyst.
 22. A catalyst for the production ofcarbon fibrils produced by the method of forming a fibril-formingcatalyst or precursors of a fibril-forming catalyst in the presence ofan effective amount of a surfactant and/or polyol to increase the yieldof the carbon fibrils and to increase the dispersion and electrochemicalproperties of the carbon fibrils; wherein said fibril-forming catalystcomprises metal particles comprising at least one of V, Nb, Ta, Cr, Mo,W, Mn, To, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt or a lanthanide andsaid metal particles are dispersed on a catalyst support particleselected from the group consisting of alumina or magnesia particles. 23.The method of claim 22, wherein said carbon fibrils have at least oneresistivity characteristic that is at least about 40% less than theresistivity characteristic of carbon fibrils produced using catalystsformed without the presence of said surfactant and/or polyol.
 24. Themethod of claim 22, wherein said carbon fibrils have at least oneresistivity characteristic that is at least about 65% less than theresistivity characteristic of carbon fibrils produced using catalystsforged without the presence of said surfactant and/or polyol.
 25. Themethod of claim 22, wherein said carbon fibrils have at least oneresistivity characteristic that is at least about 75% less than theresistivity characteristic of carbon fibrils produced using catalystsformed without the presence of said surfactant and/or polyol.
 26. Thecatalyst as recited in claim 22, wherein the formation of saidfibril-forming catalyst comprises the steps of: (a) forming an aqueoussolution of a compound comprising iron and optionally at least oneelement chosen from V, Nb, Ta, Cr, Mo, W, Mn, Tc, Re, Ru, Os, Co, Rh,Ir, Ni, Pd, Pt or the lanthanides; (b) forming a slurry of catalystsupport particles selected from the group consisting of alumina andmagnesia particles; (c) precipitating the compound of step (a) onto saidsupport particles; and (d) recovering said support particles from saidslurry to produce said fibril-forming catalyst.
 27. A method as recitedin claim 19, wherein said support particles comprise alumina particles.28. The method as recited in claim 1, wherein the metal particlescomprise iron and molybdenum.
 29. The method as recited in claim 12,wherein the compound particles comprise iron and molybdenum.
 30. Thecatalyst as recited in claim 20, wherein the metal particles compriseiron and molybdenum.
 31. The catalyst as recited in claim 20, whereinthe formation of said fibril-forming catalyst comprises the steps of:(a) forming an aqueous solution of a compound comprising iron andoptionally at least one element chosen from V, Nb, Ta, Cr, Mo, X, Mn,Tc, Re, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt or the lanthanides; (b) forming aslurry of catalyst support particles selected from the group consistingof alumina and magnesia particles; (c) precipitating the compound ofstep (a) onto said support particles; and (d) recovering said supportparticles from said slurry to produce said fibril-forming catalyst.